The walls showed that it had been cut through solid rock.
The boys listened for some indication of life or motion in the tunnel, but all was silent.

Not even a bird or creeping thing disturbed the stillness of the place.
"Shall we go in now ?" asked Nestor.
"Sure!" replied Shaw.

"We may find a well in there!" "Or a soda fountain, or a modern filter," grinned Jimmie.

"How would they ever get a well down through this mountain ?" "Water in wells comes from elevations before it gravitates to the bottom of the holes from which we pump it," Shaw declared, in defense of his suggestion.

"There may be a reservoir here somewhere." "How far is this cavern floor from the surface above it ?" asked Harry Stevens, with a judicial air.
"About four hundred feet," was the reply.